The present invention relates generally to electric power steering (EPS) systems and, more particularly, to a structure for facilitating the routing of wires and other signal transmission media used for conveying control signals to sensor and motor elements incorporated into an electric power steering (EPS) system.
There is a need to measure both the torque and the angular positions of portions of a steering shaft assembly in automotive vehicles utilizing an EPS system. Generally, the steering shaft assembly is formed from an input shaft and an output shaft coupled to the input shaft. The input and output shafts may be coupled by a torsion bar engaging both of the shafts. The input shaft is also connected to a steering wheel of the vehicle, and the output shaft is connected to a steering mechanism which turns the vehicle road wheels to provide a desired steer angle of the vehicle based on the degree of rotation of the input shaft by a driver of the vehicle.
Generally, in order to determine the degree of electro-mechanical assist needed to turn the road wheels of the vehicle, it is necessary to calculate the torque applied by a driver of the vehicle when the driver turns a steering wheel to rotate the input shaft. The torsion bar allows the input shaft to rotate with respect to the output shaft by a predetermined amount, and a torque sensor assembly senses the relative rotational movement between the input shaft and the output shaft. The torque sensor assembly sends a signal to an electronic control unit (ECU), which then sends a control signal to a motor, initiating operation of the motor. The motor powers a gear assembly coupled to the steering mechanism. This gear assembly provides assistance in turning the vehicle road wheels.
To protect the torque sensor system from exposure to the dirt, grease, heat, and moisture encountered under the hood of the vehicle while providing proximity to the steering shaft assembly, the torque sensor assembly may be enclosed inside a housing which contains the steering shaft assembly. In addition, a signal transmission medium is provided for conveying a signal from the torque sensor assembly to the ECU. Based on this signal, the ECU generates a control signal to the motor controlling the gear assembly coupled to the steering mechanism. The signal transmission medium must be routed from the torque sensor assembly to the ECU. In previous designs, sealed electrical connectors were used to pass the signal medium from the torque sensor assembly in the interior of the shaft assembly housing to an exterior of the housing, and from the exterior of the ECU housing through to the interior of the ECU housing, for connection to the ECU. However, the use of sealed connectors in routing the signal medium to the exteriors of the housings increases the labor and material costs of the EPS assembly.